Surface modification isocyanate treatment

Natural fibers are hydrophilic and do not tend to be easily wetted or bond well with many matrix materials, particularly the commodity thermoplastics. Coupling agents, such as maleated polyolefins, silanes, and isocyanates, are often necessary for adequate performance. A wide variety of coupling agents, fiber surface modifications, and treatments has been investigated for use in natural fiber plastic composites and are reviewed elsewhere [22]. 

To improve the adhesion between natural fiber and polymer matrix, chemical modification of natural fibers was investigated by a number of researchers. The mechanism and utilization of selected chemical treatments is discussed in this section. There are many different methods to improve the interfacial adhesion between fiber and matrix by modifying fiber surface such as acetylation, benzoyla-tion, acrylation, permanganate, and isocyanate treatment. These treatments are described in detail by Kalia et al. [69]. 

In order to improve the interfacial adhesion, the addition of functionalized polymers, i.e., MAPP or MAPE to the composite is employed. The presence of these polymers slightly modifies stiffness, but significantly increases tensile yield stress, tensile strength, and in some cases deformabillty [69,70], The numerous other surface modification techniques like silane treatment [71,72], isocyanates [73,74], surfactants [75], and various monomers as well as chemical modification [76,77] are also utilized. 

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